Place the Bolens BL250 on the ground or a work bench. Pull the end of the spark plug wire off the top of the spark plug.
Insert the locking rod into the hole between the spool and the bottom of the guard. The locking rod that comes with the Bolens BL250 is a 1/8-inch round dowel which is bent. If you do not have the locking rod, use a standard nail or small Phillips-head screwdriver.
Rotate the spool with one hand while holding the locking rod in your other hand. The inner shaft has a hole that the locking rod slips into when rotating the spool.
Hold the locking rod and turn the spool counterclockwise with your hand to remove it from the threaded shaft. Set the spool aside for reinstallation later.